Illustrated in copending applications U.S. Ser. No. 10/042,342, U.S. Ser. No. 10/042,356, U.S. Ser. No. 10/042,357, U.S. Ser. No. 10/042,359, U.S. Ser. No. 10/042,360, the disclosures of which are totally incorporated herein by reference, and filed concurrently herewith, all titled xe2x80x9cPolythiophenes and Devices Thereofxe2x80x9d and all filed Jan. 11, 2002, are polythiophenes and devices thereof. The appropriate components, processes thereof and uses thereof illustrated in those copending applications may be selected for the present invention in embodiments thereof.
The present invention is generally directed to polythiophenes and uses thereof. More specifically, the present invention in embodiments is directed to a class of polythiophenes wherein certain repeating thienylene units possess side chains, such as alkyl, which are arranged in a regioregular manner on the polythiophene backbone, and which polythiophenes are, for example, useful as active semiconductive materials for thin film field-effect transistors (FETs).
Semiconductive polymers like certain polythiophenes, which are useful as active semiconductor materials in thin film transistors (TFTs), have been reported. A number of these polymers have some solubility in organic solvents and are thus able to be fabricated as semiconductor channel layers in TFTs by solution processes, such as spin coating, solution casting, dip coating, screen printing, stamp printing, jet printing and the like. Their ability to be fabricated via common solution processes would render their manufacturing simpler and cost effective as compared to the costly conventional photolithographic processes typical of silicon-based devices such as hydrogenated amorphous silicon TFTs. Moreover, desired are transistors fabricated with polymer materials, such as polythiophenes, referred to as polymer TFTs, with excellent mechanical durability and structural flexibility, which may be highly desirable for fabricating flexible TFTs on plastic substrates. Flexible TFTs would enable the design of electronic devices which usually require structural flexibility and mechanical durability characteristics. The use of plastic substrates together with organic or polymer transistor components can transform the traditionally rigid silicon TFT into a mechanically more durable and structurally flexible polymer TFT design. The latter is of particular value to large area devices such as large-area image sensors, electronic paper and other display media. Also, the selection of polymer TFTs for integrated circuit logic elements for low end microelectronics, such as smart cards, radio frequency identification (RFID) tags, and memory/storage devices, may also greatly enhance their mechanical durability, and thus their useful life span. Nonetheless, many of the semiconductor polythiophenes are not, it is believed, stable when exposed to air as they become oxidatively doped by ambient oxygen, resulting in increased conductivity. The result is larger off-current and thus lower current on/off ratio for the devices fabricated from these materials. Accordingly, with many of these materials, rigorous precautions have to be undertaken during materials processing and device fabrication to exclude environmental oxygen to avoid or minimize oxidative doping. These precautionary measures add to the cost of manufacturing therefore offsetting the appeal of certain polymer TFTs as an economical alternative to amorphous silicon technology, particularly for large area devices. These and other disadvantages are avoided or minimized in embodiments of the present invention.
A number of organic semiconductor materials has been described for use in field-effect TFTs, which materials include organic small molecules such as pentacene, see for example D. J. Gundlach et al., xe2x80x9cPentacene organic thin film transistorsxe2x80x94molecular ordering and mobilityxe2x80x9d, IEEE Electron Device Lett., Vol. 18, p. 87 (1997), to oligomers such as sexithiophenes or their variants, see for example reference F. Garnier et al., xe2x80x9cMolecular engineering of organic semiconductors: Design of self-assembly properties in conjugated thiophene oligomersxe2x80x9d, Amer. Chem. Soc., Vol. 115, p. 8716 (1993), and certain polythiophenes, such as poly(3-alkylthiophene), see for example reference Z. Bao et al., xe2x80x9cSoluble and processable regioregular poly(3-hexylthiophene) for field-effect thin film transistor application with high mobilityxe2x80x9d, Appl. Phys. Lett. Vol. 69, p4108 (1996). Although organic material based TFTs generally provide lower performance characteristics than their conventional silicon counterparts, such as silicon crystal or polysilicon TFTs, they are nonetheless sufficiently useful for applications in areas where high mobility is not required. These include large area devices, such as image sensors, active matrix liquid crystal displays and low end microelectronics such as smart cards and RFID tags. TFTs fabricated from organic or polymer materials may be functionally and structurally more desirable than conventional silicon technology in the aforementioned areas in that they may offer mechanical durability, structural flexibility, and the potential of being able to be incorporated directly onto the active media of the devices, thus enhancing device compactness for transportability. However, most small molecule or oligomer-based devices rely on difficult vacuum deposition techniques for fabrication. Vacuum deposition is selected primarily because the small molecular materials are either insoluble or their solution processing by spin coating, solution casting, or stamp printing do not generally provide uniform thin films. In addition, vacuum deposition may also involve the difficulty of achieving consistent thin film quality for large area format. Polymer TFTs, such as those fabricated from regioregular polythiophenes of, for example, regioregular poly(3-alkylthiophene-2,5-diyl) by solution processes, while offering some mobility, suffer from their propensity towards oxidative doping in air. For practical low cost TFT design, it is therefore of value to have a semiconductor material that is both stable and solution processable, and where its performance is not adversely affected by ambient oxygen, for example, regioregular polythiophenes such as poly(3-alkylthiophene-2,5-diyl) are very sensitive to air. The TFTs fabricated from these materials in ambient conditions generally exhibit very large off-current, very low current on/off ratios, and their performance characteristics degrade rapidly.
References that may be of interest include U.S. Pat. Nos. 6,150,191; 6,107,117; 5,969,376; 5,619,357, and 5,777,070.
Illustrated in FIGS. 1 to 4 are various representative embodiments of the present invention and wherein polythiophenes are selected as the channel materials in thin film transistor (TFT) configurations.
It is a feature of the present invention to provide semiconductor polymers such as polythiophenes, which are useful for microelectronic device applications, such as TFT devices.
It is another feature of the present invention to provide polythiophenes with a band gap of from about 1.5 eV to about 3 eV as determined from the absorption spectra of thin films thereof, and which polythiophenes are suitable for use as TFT semiconductor channel layer materials.
In yet a further feature of the present invention there are provided polythiophenes which are useful as microelectronic components, and which polythiophenes have reasonable solubility of, for example, at least about 0.1 percent by weight in common organic solvents, such as methylene chloride, tetrahydrofuran, toluene, xylene, mesitylene, chlorobenzene, and the like, and thus these components can be economically fabricated by solution processes such as spin coating, screen printing, stamp printing, dip coating, solution casting, jet printing, and the like.
Another feature of the present invention resides in providing electronic devices, such as TFTs with a polythiophene channel layer, and which layer has a conductivity of from about 10xe2x88x926 to about 10xe2x88x929 S/cm (Siemens/centimeter).
Also, in yet another feature of the present invention there are provided polythiophenes and devices thereof, and which devices exhibit enhanced resistance to the adverse effects of oxygen, that is, these devices exhibit relatively high current on/off ratios, and their performance does not substantially degrade as rapidly as similar devices fabricated from regioregular polythiophenes such as regioregular poly(3-alkylthiophene-3,5-diyl).
Additionally, in a further feature of the present invention there is provided a class of polythiophenes with unique structural features which are conducive to molecular self-alignment under appropriate processing conditions, and which structural features also enhance the stability of device performance. Proper molecular alignment can permit higher molecular structural order in thin films, which can be important to efficient charge carrier transport, thus higher electrical performance.
There are disclosed in embodiments polythiophenes and electronic devices thereof. More specifically, the present invention relates to polythiophenes illustrated by or encompassed by Formula (I) 
wherein, for example, R is a side chain comprising, for example, alkyl, alkyl derivatives, such as alkoxyalkyl; siloxy-subsituted alkyl, perhaloalkyl, such as a perfluoro, polyether, such as oligoethylene oxide, polysiloxy, and the like; A is a divalent linkage selected, for example, from the group consisting of arylene such as phenylene, biphenylene, phenanthrenylene, dihydrophenanthrenylene, fluorenylene, oligoarylene, methylene, polymethylene, dialkylmethylene, dioxyalkylene, dioxyarylene, oligoethylene oxide, and the like; m is the number of side chains, for example 1 or 2; x and y are the numbers of the R substituted thienylenes and the non-substituted thienylene moieties, respectively; and z is the number of divalent linkages and is usually 0 or 1; the relative positions of the R substituted and non-substituted thienylene moieties, and the divalent linkage; and n represents the number of segments. A in the monomer segment may be different from those presented in Formula (I), that is for example, polythiophenes (I) schematically represented by Formula (II) as semiconductor layers in TFT devices: 
wherein R is a side chain comprised of, for example, alkyl derivatives, such as alkoxyalkyl, siloxy-subsituted alkyl, perhaloalkyl, such as perfluoro, polyether, such as oligoethylene oxide, polysiloxy derivatives, and the like; a is an integer (or number) of from about 0 to about 5; b, c, and d are integers of from about 1 to about 5; and n is the degree of polymerization, and can be from about 5 to over 5,000, and more specifically, from about 10 to about 1,000 wherein the number average molecular weight (Mn) of the polythiophenes can be, for example, from about 2,000 to about 100,000, and more specifically, from about 4,000 to about 50,000, and the weight average molecular weight (Mw) thereof can be from about 4,000 to about 500,000, and more specifically, from about 5,000 to about 100,000 both as measured by gel permeation chromatography using polystyrene standards. Examples of the side chains for the polythiophenes (I) and (II) include alkyl with, for example, from about 1 to about 25, and more specifically, from about 4 to about 12 carbon atoms (included throughout are numbers within the range, for example 4, 5, 6, 7, 8, 9, 10, 11 and 12), such as butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, isomeric forms thereof, mixtures thereof, and the like; alkoxyalkyl with, for example, from about 2 to about 30 carbon atoms, such as for example methoxypropyl, methoxybutyl, methoxyhexyl, methoxyhexyl, methoxyheptyl, and the like, polyether chains, such as polyethylene oxide; perhaloalkyl, such as perfluoroalkyl, polysiloxy chain, such as trialkylsiloxyalkyl derivatives, and the like.
Specific illustrative polythiophenes examples are wherein n is as illustrated herein. 
The polythiophenes in embodiments are soluble in common coating solvents, for example, in embodiments they possess a solubility of at least about 0.1 percent by weight, and more specifically, from about 0.5 percent to about 5 percent by weight in such solvents as methylene chloride, 1,2-dichloroethane, tetrahydrofuran, toluene, xylene, mesitylene, chlorobenzene, and the like. Moreover, the polythiophenes of the present invention in embodiments when fabricated as semiconductor channel layers in TFT devices provide a stable conductivity of, for example, from about 10xe2x88x929 S/cm to about 10xe2x88x926 S/cm, and more specifically, from about 10xe2x88x928 S/cm to about 10xe2x88x927 S/cm as determined by conventional four-probe conductivity measurements. Further, the polythiophenes (II) include side chains that are regioregularly positioned on the polythiophene backbone, reference Formulas m that follow, and in which four polymer chains of polythiophene (II-e) are schematically represented. The strategically positioned side chains in (II) facilitate proper alignment of side chains which enables formation of higher ordered microstructure domains in thin films. It is believed that these polythiophenes when fabricated from solutions as thin films of, for example, about 10 nanometers to about 500 nanometers form closely stacked lamella structures that are conducive to efficient charge carrier transport. The incorporated unsubstituted thienylene moieties in (II) have some degree of rotational freedom, which helps to disrupt the extended xcfx80-conjugation of the polythiophene system to an extent that is sufficient to suppress its propensity towards oxidative doping. Accordingly, these materials are more stable in ambient conditions and the devices fabricated from these polythiophenes are functionally more stable than that of regioregular polythiophenes such as regioregular poly(3-alkylthiophene-2,5-diyl). When unprotected, the aforementioned stable materials and devices are generally stable for a number of weeks rather than days or hours as is the situation with regioregular poly(3-alkylthiophene-2,5-diyl) after exposure to ambient oxygen, thus the devices fabricated from the polythiophenes in embodiments of the present invention can provide higher current on/off ratios, and their performance characteristics do not substantially change as rapidly as that of poly(3-alkylthiophene-2,5-diyl) when no rigorous procedural precautions have been taken to exclude ambient oxygen during material preparation, device fabrication, and evaluation. The polythiophene stability of the present invention in embodiments against oxidative doping, particularly for low cost device manufacturing, do not usually have to be handled in an inert atmosphere and the processes thereof are, therefore, simpler and more cost effective, and the fabrication thereof can be applied to large scale production processes. 
The preparation of polythiophenes of the present invention can be illustrated with reference to the preparation of polythiophene (IV) from a suitably constructed oligothiophene monomer, such as (IIIa) or (IIIb), according to the general processes depicted in Scheme 1. Polythiophene (IV) is a member of polythiophene (II) wherein a=0, b=d=1. Monomer (IIIa) can readily be obtained from the reaction of 3-R-thienyl-2-magnesiumbromide with 5,5xe2x80x2-dibromo-2,2xe2x80x2-dithiophene. Monomer (IIIa) or (IIIb) possess side chains which are strategically placed on the terminal thienylene units so that when polymerized the resultant polythiophene (IV) possesses side chains which are regioregularly positioned on its backbone. Unlike the preparation of regioregular polythiophenes, such as poly(3-alkylthiophene-2,5-diyl) which require regioregular coupling reaction, the polythiophenes of the present invention can be prepared by general polymerization techniques without regioregularity complications. Specifically, FeCl3 mediated oxidative coupling of (IIIa) has been successfully utilized in the preparation of polythiophenes (IV). 
NBS: N-Bromosuccinimide
Ni(dppe)Cl2: [1,2-Bis(diphenylphosphinoethane)]dichloronickel (II)
The polymerization is generally conducted by adding a solution of 1 molar equivalent of (IIIa) in a chlorinated solvent, such as chloroform, to a suspension of about 1 to about 5 molar equivalents of anhydrous FeCl3 in the same chlorinated solvent. The resultant mixture was permitted to react at a temperature of about 25xc2x0 C. to about 60xc2x0 C. under a blanket of dried air or with a slow stream of dried air bubbling through the reaction mixture for a period of about 30 minutes to about 48 hours. After the reaction, the polymer product can be isolated by washing the reaction mixture with water or a dilute aqueous hydrochloric acid solution, stirring with a dilute aqueous ammonium solution for a period of about 15 minutes to one hour, followed by washing with water, precipitation from a nonsolvent, and optionally extracting the polythiophene product via soxhlet extraction with appropriate solvents such as methanol, toluene, xylene, chlorobenzene, and the like. The polythiophene product thus obtained can be further purified by precipitation from a suitable solvent such as methanol or acetone.
Aspects of the present invention relate to an electronic device containing a polythiophene 
wherein R represents a side chain, m represents the number of R substituents; A is a divalent linkage; x, y and z represent, respectively, the number of Rm substituted thienylenes, unsubstituted thienylenes, and divalent linkages A, respectively, in the monomer segment subject to z being 0 or 1, and n represents the number of repeating monomer segments in the polymer or the degree of polymerization; a device which is a thin film transistor (TFT) comprised of a substrate, a gate electrode, a gate dielectric layer, a source electrode and a drain electrode, and in contact with the source/drain electrodes and the gate dielectric layer semiconductor a layer comprised of polythiophene wherein R is alkoxyalkyl, siloxy-subsituted alkyl, a perhaloalkyl, or a polyether; A is a divalent linkage selected from the group consisting of arylene of about 6 to about 40 carbon atoms; m is 1 or 2; x and y are the number of the R substituted thienylenes and the unsubstituted thienylene moieties, respectively, each of which are from 1 to 5; z is zero or 1, and represents the number of divalent linkages; and n represents the number of monomer segments; a device wherein n is from about 5 to about 5,000; the number average molecular weight (Mn) of the polythiophene is from about 2,000 to about 100,000; the weight average molecular weight (Mw) is from about 4,000 to over 500,000, both Mw and Mn being measured by gel permeation chromatography using polystyrene standards; a device wherein R is alkyl containing from 1 to about 20 carbon atoms, and wherein n is from about 10 to about 1,000; the Mn is from about 4,000 to about 50,000; and the Mw is from about 5,000 to about 100,000; a device wherein the alkyl side chain R contains from 6 to about 12 carbon atoms; a device wherein the alkyl side chain R is butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, or dodecyl; a device wherein the side chain R is a perfluoroalkyl of about 2 to about 15 carbon atoms; a device wherein the side chain R is siloxyalkyl of trimethylsiloxyalkyl, triethylsiloxyalkyl, and wherein alkyl optionally contains from about 4 to about 10 carbons, and which alkyl is butyl, pentyl, hexyl, heptyl, or octyl; a device wherein the divalent linkage A is an arylene with from about 6 to about 40 carbon atoms; a TFT device wherein the divalent linkage A is selected from the group consisting of phenylene, biphenylene, phenanthrenylene, 9,10-dihydrophenanthrenylene, fluorenylene, methylene, polymethylene, dioxyalkylene, dioxyarylene, and oligoethylene oxide; a thin film transistor containing said polythiophene is represented by 
wherein R is a side chain; a, b, c, and d represent the number of thienylene moieties; and n is the degree of polymerization; a device wherein R is alkyl containing from about 1 to about 20 carbon atoms; a device wherein R is alkyl containing from about 6 to about 12 carbon atoms; a device wherein R is butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, or dodecyl; a device wherein b and d are from about 1 to about 5; a device wherein b and d are from about 1 to about 3; a device wherein a is from about 0 to about 5, and c is about 1 to about 5, or wherein a is about 0 to about 3, and c is about 1 to about 3; a thin film transistor containing a polythiophene represented by Formula (IV) 
a thin film transistor device containing a polythiophene selected from the group consisting of polythiophenes (II-a) through (II-o) 
a thin film transistor containing a polythiophene selected from the group consisting of (II-a) through (II-e) 
a thin film transistor containing a polythiophene selected from the group consisting of (II-a) through (II-e) 
a device wherein n is a number of from about 5 to about 3,000; a device wherein n is a number of from about 5 to about 3,000; a device wherein n is a number of from about 5 to about 5,000; a device wherein R is hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, or pentadecyl, and the like; and m=1, x=y=2, z=0 or 1; a device wherein R is hexyl, heptyl, octyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, or pentadecyl, and m=1, x=y=2, and z=0 or 1; a device wherein the polythiophene selected possesses a Mn of from about 2,000 to about 100,000, and a Mw of from about 4,000 to about 500,000; a device wherein the polythiophene possesses a Mn of from about 2,000 to about 100,000, and a Mw of from about 4,000 to about 1,000,000; a device wherein the polythiophene is selected from the group consisting of (II-a) through Formula (II-e), and wherein n is a number of from about 50 to about 3,000
a TFT device wherein the substrate is a plastic sheet of a polyester, a polycarbonate, or a polyimide; the gate source and drain electrodes are each independently comprised of gold, nickel, aluminum, platinum, indium titanium oxide, or a conductive polymer, and the gate is a dielectric layer comprised of silicon nitride or silicon oxide; a TFT device wherein the substrate is glass or a plastic sheet; said gate, source and drain electrodes are each comprised of gold, and the gate dielectric layer is comprised of the organic polymer poly(methacrylate), or poly(vinyl phenol); a device wherein the polythiophene layer is formed by solution processes of spin coating, stamp printing, screen printing, or jet printing; a device wherein the gate, source and drain electrodes, the gate dielectric, and semiconductor layers are formed by solution processes of spin coating, solution casting, stamp printing, screen printing, or jet printing; and a TFT device wherein the substrate is a plastic sheet of a polyester, a polycarbonate, or a polyimide, and the gate, source and drain electrodes are fabricated from the organic conductive polymer polystyrene sulfonate-doped poly(3,4-ethylene dioxythiophene) or from a conductive ink/paste compound of a colloidal dispersion of silver in a polymer binder, and the gate dielectric layer is organic polymer or inorganic oxide particle-polymer composite; device or devices include electronic devices such as TFTs.